Description:
The NSLS-II is a new ultra-bright 3rd generation 3 GeV light source that will be built at Brookhaven National Laboratory. Its design is well under way. The requirements for the compact injector complex, which will continuously provide 3 GeV electrons for top-off injection into the storage ring, are demanding: high reliability, relatively high charge and low losses. The injector consists of a linear accelerator, a full-energy booster, as well as transport lines, and an injection straight section. In this paper we give an overview of the NSLS-II injector, discuss its status, specifications, and the design challenges.

Description:
NSLS booster diagnostics consisted of tune measurement system, system for turn-by-turn measurement on the electron beam, and beam intensity monitor, which is not absolutely calibrated. We present design and implementation of synchrotron light monitor for the booster, which expands diagnostics capabilities. The system allows to measure an orbit, beam sizes and coupling of the electron beam along the ramp.

Description:
One of the problems in the high-power lasers design is in outcoupling of a powerful laser beam out of a vacuum volume into atmosphere. Usually the laser device is located inside a vacuum tank. The laser radiation is transported to the outside world through the transparent vacuum window. While considered transparent, some of the light passing through the glass is absorbed and converted to heat. For most applications, these properties are academic curiosities; however, in multi-kilowatt lasers, the heat becomes significant and can lead to a failure. The absorbed power can result in thermal stress, reduction of light transmission and, consequently, window damage. Modern optical technology has developed different types of glass (Silica, BK7, diamond, etc.) that have high thermal conductivity and damage threshold. However, for kilo- and megawatt lasers the issue still remains open. In this paper we present a solution that may relieve the heat load on the output window. We discuss advantages and issues of this particular window design.

Description:
In the following text we analyze and compare results of the two publications ([1], [2]), dedicated to development of the tunable high-gain Free Electron laser (FEL), seeded by an external source. As a conclusion we summarize similarities and differences between these concepts. This note is initiated by the polemics on the similarity of two different schemes of the wavelength tuning in a seeded high-gain FEL. Below we will be calling the scheme, presented by S. Biedron, S, Milton and H. Freund in Nuclear Instruments and Methods of 2001 ([1]), as the first (1st) scheme. The scheme that we developed and presented in the BNL preprint ([2]) will be called as the second (2nd) scheme. The following analysis provides important information on similarities and differences between both techniques. We start by considering the first approach. As we understand, the goal of the Modular Approach is to make X-ray FEL design more flexible [1]. Usual linac-based FELs begin from a long linac with bunch compressor(s) followed by an FEL magnetic system. The essence of the Modular Approach is to break a machine into modules and then recombine these modules in a more efficient way (from the point of view of monetary and/or time constraints). The chapter 3.5 of [1] presents some basic example of Modular Approach. We have studied the scheme, discussed in [1] and illustrated in Fig. 2. Even though very few details of the scheme were presented, it was still sufficient to obtain a complete qualitative picture. Let us begin with the usual phase space of the microbunched beam, which enters a radiator in a prebunched FEL (Fig. 1). The sharp spike (in blue) represents the longitudinal density bunching, which will be the main subject of interest in this discussion. The key principle of a seeded high-gain FEL optimization is ...

Description:
Third generation light sources require top-off operation in order to provide high stability of the photon beam. In this paper we present a conceptual design of the fast pulsed magnets used for injection into the 3 GeV storage ring. Because the NSLS-II project is in the design stage possible variants of the injection straight section are also discussed.

Description:
The goals of the Workshop are to assess the design of pulsed system at the NSLS-II and establish mitigation strategies for critical issues during development. The focus of the Workshop is on resolving questions related to the set-up of the pulsed magnet laboratory, on measuring the pulsed magnet's current waveforms and fields, and on achieving tight tolerances on the magnet's alignment and field quality.

Description:
The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme. We show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The injectors must provide 7.5nC in bunch trains 80-150 bunches long every minute for top off operation of the storage ring. Top off then requires that the linac deliver 15nC of charge once losses in the injector chain are taken into consideration. This is a very stringent requirement that has not been demonstrated at an operating light source. For this reason we have developed a method to transversely stack two bunch trains in the booster while maintaining the charge transport efficiency. This stacking scheme has been discussed previously. In this paper we show the simulations of the booster ramp with a single bunch train in the booster. Then we give a brief overview of the stacking scheme. Following, we show the results of stacking two bunch trains ...

Description:
The NSLS-II light source which is a proposed facility to be built at Brookhaven National Laboratory utilizes two synchrotron accelerator rings: the booster and the Storage ring (SR). Designing the NSLS-11 injector we considered two options for the booster layout, where the rings either (a) share the same tunnel, but placed at different horizontal planes or (b) booster is located in a separate building. The booster which accepts beam from the linac, accelerates the electron beam to an energy of 3.0 GeV and the beam is extracted to the Booster to Storage Ring (BtS) transport line which transports the beam and injects it into the SR ring. The design procedure for each of the two options of the BtS line and other details about the optics and the magnetic elements of the line are presented in this paper.

Description:
The orbit bumps in NSLS booster are used to move the beam orbit within 2mm of the extraction septum aperture on a time scale of millisecond at extraction in order to reduce the requirement on the amplitude of the fast extraction kicker. This may cause charge losses since before extraction, the beam stays on the distorted orbit for thousands of revolutions. In order to find the optimal orbit bump setpoint, which brings the maximum distortion at the extraction position and minimum distortions everywhere else, we developed an extraction model and performed an experiment to validate it. Afterwards, the model was applied to optimize the extraction process.

Description:
The National Synchrotron Light Source is performing R&amp;D of a new 3 GeV electron storage ring to be used for the facility upgrade [1]. To satisfy the demands for the brightness and stability of the future light source a state-of-the-art diagnostics system is a necessity. We present our preliminary design with focus on the requirements for instrumentation and technical solutions to achieve them.

Description:
We present preliminary experimental results on evolution of properties of the DUV FEL [1,2] radiation along the radiator. Intercepting the electron beam at the different locations inside the undulator we recorded and analyzed transverse profiles, spectra and intensity of the FEL output. Shot-to-shot fluctuations of the FEL radiation may significantly affect the accuracy of measurement. In the paper we present and discuss a single-shot measurement technique, based on a special imaging system.

Description:
As was discussed earlier [1,2] longitudinal space charge force in initially nonuniform bunch transforms density fluctuations into energy modulation along the bunch. For characterization of the resulted energy modulation one can chirp the bunch using accelerator section, located upstream of beam spectrometer, and record energy spectrum of such chirped bunch. Measured spectrum shows structure with parameters, depending on the bunch properties. In this paper we present analysis of the structure in the bunch energy spectrum and its connection with energy modulation along the bunch.

Description:
The Linac Front End Test Stand (LFETS) was installed at the Source Development Laboratory (SDL) in the fall of 2011 in order to test the Linac Front End. The goal of these tests was to test the electron source against the specifications of the linac. In this report, we discuss the results of these measurements and the effect on linac performance.

Description:
The NSLS-II operational parameters place very stringent requirements on the injection system. Among these are the charge per bunch train at low emittance that is required from the linac along with the uniformity of the charge per bunch along the train. The NSLS-II linac is a 200 MeV linac produced by Research Instruments Gmbh. Part of the strategy for understanding to operation of the injectors is to test the front end of the linac prior to its installation in the facility. The linac front end consists of a 100 kV electron gun, 500 MHz subharmonic prebuncher, focusing solenoids and a suite of diagnostics. The diagnostics in the front end need to be supplemented with an additional suite of diagnostics to fully characterize the beam. In this paper we discuss the design of a test stand to measure the various properties of the beam generated from this section. In particular, the test stand will measure the charge, transverse emittance, energy, energy spread, and bunching performance of the linac front end under all operating conditions of the front end.

Description:
The NSLS II linac will produce a bunch train, 80-150 bunches long with 2 ns bunch spacing. Having the ability to tailor the bunch train can lead to the smaller bunch to bunch charge variation in the storage ring. A stripline is planned to integrate into the linac baseline to achieve this tailoring. The stripline must have a fast field rise and fall time to tailor each bunch. The beam dynamics is minimally affected by including the extra space for the stripline. This paper discusses the linac beam dynamics with stripline, and the optimal design of the stripline. A stripline is to be integrated in the linac to match the storage ring uniform bunch charge requirement, which simplifies the gun pulser electronics and looses the edge uniform requirement. It is located at low energy to lower the stripline power supply requirement and limit the dumped electron radiation. By turning off the stripline, the beam dynamics through linac is comparable with the baseline design. More advanced ideas can be explored. If a DC corrector along with the stripline is used, the core bunch trains gets kick from the stripline while the head and the tail of bunch train just gets a DC kick. The stripline power supply waveform is a single flat top waveform with fast rise and drop and the pulse length is {approx}200 ns long or 100 bunches, which may be easier from the power supply view point. We are also considering the bunch by bunch charge manipulation to match the storage ring uniform bunch charge distribution requirement. By modulating the flat top waveform at 250 MHz with adjustable amplitude, each the bunch center is either at 45 degree or 135 degree. Only the head or tail of the bunch is trimmed out. Although each bunch center deviation from ...

Description:
NSLS-II is a medium energy storage ring of 3GeV electron beam energy with sub-nm.rad horizontal emittance and top-off capability at 500mA. Damping wigglers will be used not only to reduce the beam emittance but also for broadband sources for users. Cryo-Permanent Magnet Undulators (CPMUs) are considered for hard X-ray linear device, and permanent magnet based Elliptically Polarized Undulators (EPUs) are for polarization control. Rigorous R&amp;D plans have been established to pursue the performance enhancement of the above devices as well as building new types of insertion devices such as high temperature superconducting wiggler/undulators. This paper describes the details of these activities and discuss technical issues.

Description:
We present the results of electron beam longitudinal modulation studies in the DUV-FEL accelerator. For bunch length determination we used the 'zero-phasing' method, based on a measurement of the chirped electron bunch energy spectra. The measurements revealed a spiky structure in the longitudinal phase space [1]. A model based on space charge effect is considered [2] to explain of the obtained phenomena. The analysis of the energy spectra has shown a sensitivity of the structure to the electron beam peak current, energy and longitudinal non-uniformity of the RF gun drive laser. Analytical calculations have demonstrated a qualitative agreement with experimental observations. Several experiments have been made to compare with theory; measured results are reviewed in this paper. The obtained effect is briefly discussed in relation to high brightness accelerators.

Description:
The NSLS-II is a state of the art 3 GeV synchrotron light source being developed at BNL. The injection system will consist of a 200 MeV linac and a 3 GeV booster synchrotron. The injection system must supply 7.3 nC every minute to satisfy the top off requirements. A large booster acceptance is necessary to have a high booster injection efficiency and alleviate the requirements on the linac gun. We also anticipate transverse stacking of bunches in the booster to increase the amount of charge that can be delivered. We present studies of the anticipated booster stay clear and the ramifications for injection efficiency and transverse stacking.

Description:
Currently the facility upgrade project is in progress at the NSLS (at Brookhaven National Laboratory). The goal of the NSLS-II is a 3 GeV ultra-low-emittance storage ring that will increase radiation brightness by three orders of magnitude over that of the present NSLS X-ray ring. The low emittance of the high brightness ring's lattice results in a short lifetime, so that a top-off injection mode becomes an operational necessity. Therefore, the NSLS-II injection system must provide, and efficiently inject, an electron beam at a high repetition rate. In this paper, we present our concept of the NSLS-II injection system and discuss the conditions for, and constraints on, its design.

Description:
The ultra-bright light source being developed by the NSLS-II project will utilize top-up injection and fine tuning of the injection process is mandatory. In this paper we present the diagnostics installed in the injection straight. Its use for commissioning and tuning of the injection cycle is also described. The NSLS-II storage ring will utilize a 9.3 meter long injection straight section shown in Fig. 1. Injection will be preformed with two septa (one pulsed, one DC) and four kickers. The stored beam will be shifted towards the pulsed septum up to IS mm and the nominal distance between centers of the injected and the bumped beam is 9.5mm. The NSLS-II beam position monitors will have turn-by-turn and first-turn capabilities and will be used for the commissioning and tuning the injection process. However, there are three additional BPMs and two beam intercepting OTR screens (flags) installed in the injection straight.

Description:
The NSLS II beam injection works with a DC septum, a pulsed septum and four fast kicker magnets. The kicker power supplies each produce a two revolution period pulsed field, 5.2 {micro}s half sine waveform, using {approx}5kA drive voltage. The corresponding close orbit bump amplitude is {approx}15mm. It is desired that the bump is transparent to the users for top-off injection. However, high voltage and short pulse power supplies have challenges to maintain pulse-to-pulse stability and magnet-to-magnet reproducibility. To minimize these issues, we propose implementing a DC local bump on top of the fast bump to reduce the fast kicker strength by a factor of 2/3. This bump uses two storage ring corrector magnets plus one additional magnet at the septum to create a local bump. Additionally, these magnets could provide a DC bump to simulate the septum position effects on the store beam lifetime. This paper presents the detail design of this DC injection bump and related beam dynamics.

Description:
We discuss an upgrade R&amp;D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. We discuss its basic parameters and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring. There is a rapid growth of ultrafast user community interested in science using sub-pico-second x-ray pulses. In BNL's Short Pulse Workshop, the discussion from users shows clearly the need for a sub-pico-second pulse source using laser slicing method. In the proposal submitted following this workshop, NSLS team proposed both hard x-ray and soft x-ray beamlines using laser slicing pulses. Hence there is clearly a need to consider the R&amp;D efforts of laser slicing short pulse generation at NSLSII to meet these goals.

Description:
The NSLS-II is a state of the art 3 GeV synchrotron light source being developed at BNL. The injection system will consist of a 200 MeV linac, 3 GeV booster synchrotron, and associated transfer lines. The transport lines between the linac and booster (LtB) and the booster and storage ring (BSR) must satisfy a number of requirements. In addition to transporting the beam while maintaining the beam emittance, these lines must allow for commissioning, provide appropriate diagnostics, allow for the appropriate safety devices and in the case of the BSR line, provide a stable beam for top off injection. Appropriate diagnostics are also necessary in the linac and booster to complement the measurements in the transfer lines and to allow for fast commissioning. In this paper we discuss the design of the transfer lines for the NSLSII along with the incorporated diagnostics and safety systems. Necessary diagnostics in the linac and booster are also discussed.

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